I've seen some PCB's with components mounted at multiples of 45 degrees (45, 135, etc.) I recently discovered my PCB program (gEDA PCB) supports these, though it isn't a GUI function and you have to run a command. When is it appropriate to mount at these angles? And what about angles of 30 degrees and 60 degrees, or arbitrary angles?

\$\begingroup\$I've actually seen arbitrary angles on a motherboard before. The RAM sockets were mounted at about 15 degrees in the middle of the motherboard (not a high performance computer, it was designed to be small.)\$\endgroup\$
– Thomas ONov 1 '10 at 20:39

Parts can be at whatever angle they need to be to help layout or fit into some bizarre package. Your manufacturing engineer may not like it, but if it's required, then oh well. As Duane mentions, this is rarely a problem nowadays, but be sure.

Conversely, your manufacturing engineer will pretty much demand 45° rotation of QFPs if they are to be wave soldered.

\$\begingroup\$Fascinating. All the wave soldering I've seen has been on the underside of a board with through-hole components on the top. But, the first PDF you linked to definitely references wave soldering QFP components. I can't imagine why the plastic package doesn't melt as you run it through the solder wave. Anyone know how this works?\$\endgroup\$
– pingsweptNov 2 '10 at 0:13

5

\$\begingroup\$Wave solder temp won't be much different to reflow, and may actually be exposed for less time. A particular issue is the higher rate-of-rise which can cause popcorning damage due to trapped moisture, but it would take a lot more to melt the plastic used for IC packages.\$\endgroup\$
– mikeselectricstuffNov 2 '10 at 0:32

Inductors and magnetics that may generate fields are recommended to be offset from one another. As an example, don't line up L1, L2 and L3 next to each other. Place L1 as you normally would, L2 at right angles to L1 and L3 at a 45 degree angle. I took this example directly off a datasheet but forget whose (Microchip, I believe).

\$\begingroup\$Uhm, it can. Try the command ":FreeRotateBuffer(45)" when something is copied into the buffer. You need a new version to do this (I have 20091103), but it does work with squares. I do wish it were broken out to the UI though.\$\endgroup\$
– Thomas ONov 2 '10 at 7:51

\$\begingroup\$Yup - you can rotate footprints to arbitrary values, you can even rotate less than a degree, If you want text at an arbitrary angle you can import a converted Postscript file, GEDA PCB can be very powerful and versatile and does far more than just "simple rectilinear designs" - if you can be bothered to learn it\$\endgroup\$
– JimNov 2 '10 at 12:49

9

\$\begingroup\$I am familiar with the PostScript converter. I wrote it.\$\endgroup\$
– markragesNov 2 '10 at 14:43

\$\begingroup\$Here's why squares rotated at 45 degrees don't work in pcb. pcb.gpleda.org/pcb-cvs/pcb.html#ElementLine-syntax Lines are marked by their start and end points, and the line width. A square is a line with identical start and end points. Therefore, the orientation of the square is not able to be captured by the file format.\$\endgroup\$
– markragesNov 2 '10 at 14:59

1

\$\begingroup\$Only Pins, Pads, ElementLines and ElementArcs are allowed within Elements. No Polys. Therefore a rect or poly will not work. Nor will a poly clear soldermask, if you were thinking about faking it that way.\$\endgroup\$
– markragesNov 2 '10 at 17:16

When you want to wave solder (not much done anymore) QFP parts you simply have to place them at a 45 degree angle. If you place them orthogonally the solder wave will short all the pins transversal to the wave. 45 degrees allows to place solder thieves that take any excess solder.